The Hidden Companion in J1527: A 0.69 Solar-mass White Dwarf?

Finding nearby neutron stars can probe the supernova and metal-enrichment histories near our solar system. Recently, Lin et al. reported an exciting neutron star candidate, Two Micron All Sky Survey J15274848+3536572 (hereafter J1527), with a small Gaia distance of 118 pc. They claim that J1527 harbors an unseen neutron star candidate with an unusually low mass of 0.98 +/- 0.03 M circle dot. In this work, we use the Canada-France-Hawaii Telescope high-resolution spectrum to measure J1527's orbital inclination independently. Our spectral fitting suggests an orbital inclination of 63 degrees +/- 2 degrees. Instead, by fitting a complex hybrid variability model consisting of the ellipsoidal-variation component and the starspot modulation to the observed light curve, Lin et al. obtain an orbital inclination of 45.2-0.20+0.13 degrees. We speculate that the orbital inclination obtained by the light-curve fitting is underestimated since J1527's light curves are obviously not pure ellipsoidal variations. According to our new inclination (i similar to 63 degrees), the mass of the unseen compact object is reduced to 0.69 +/- 0.02 M circle dot, which is as massive as a typical white dwarf.